in Communications in Agricultural and Applied Biological Sciences (in press)

The different steps of the foraging process of wireworms (Coleoptera: Elateridae) would be better understood if accurate and holistic information regarding the role of plant-produced chemicals ... [more ▼]

The different steps of the foraging process of wireworms (Coleoptera: Elateridae) would be better understood if accurate and holistic information regarding the role of plant-produced chemicals constituting their environment were available. Volatile organic compounds (VOC) play important roles in the interactions between plants and insects in many ecosystems, whether they take place aboveground or belowground. The roles of VOC are still relatively unknown for wireworms, and deserve attention. Here, we performed three experimentations with barley roots as baits. In the two first, we assessed the effect of chopped roots and fungus infected roots on the orientation of wireworms. In the third experiment, the larvae were confronted to both healthy and fungus infected roots. We discuss the results in terms of suitability of the olfactometers we designed for the investigation of olfaction in wireworms, and we provide suggestions to improve their use. [less ▲]

The tomato leafminer, Tuta absoluta (Lepidoptera: Gelechiidae), is a widespread devastating pest reported to develop on economically important solanaceous plants. The characterization of its effective ... [more ▼]

The tomato leafminer, Tuta absoluta (Lepidoptera: Gelechiidae), is a widespread devastating pest reported to develop on economically important solanaceous plants. The characterization of its effective host range could help to understand and prevent the dispersion behavior of the insect in the environment. In this study, the ability of T. absoluta to locate and develop on wild (Solanum nigrum, Atropa belladonna, Datura stramonium) and cultivated (Solanum tuberosum) solanaceous plant species under laboratory conditions was assessed. Dual-choice behavioral assays performed in flying tunnels (S. tuberosum versus another plant) revealed that adult distribution and female oviposition did not differ between Solanum species, which were preferred to the other tested plants. The volatile molecules released by each tested plant species provide some explanations in the observed behavioral discrimination: S. nigrum and S. tuberosum volatile profiles were similar, and were presenting quantitative and qualitative differences with the other tested Solanaceous plants. To determine whether the host plant choice was adaptive or not, we have finally conducted fitness assays, by rearing T. absoluta larvae on each plant species and have shown that Solanum species allowed higher larval survivability and lower development time (from egg to adult emergency) compared to the other plants. We conclude that Solanum species are suitable host plants for T. absoluta, but other Solanaceous plant species could be opportunistically colonized with fewer incidences. [less ▲]

The tomato leafminer, Tuta absoluta (Lepidoptera: Gelechiidae), is a widespread invasive species damaging economically important cultivated solanaceous crop plants, including tomatoes and potatoes. Little is known about the ability of this microlepidoptera to encounter and develop on alternative wild and agricultural plant species. These plants could provide refuges and have to be identified for more efficient integrated management strategies. In the present study, we assessed under laboratory conditions the ability of T. absoluta to develop on such plant species referred as potential hosts in the literature, including Solanaceae, Chenopodiaceae, Convolvulaceae, Fabaceae, and Malvaceae. For each plant species, fitness tests were performed in Petri dishes by isolating single individuals with excised leaf. We found that Solanum species allowed higher larval survivability and shorter development time (from egg to adult emergency) compared to the other plants. Non-solanaceous plants were not able to sustain T. absoluta larvae. Two choice behavioral assays performed in flying tunnels revealed that adult distribution and female oviposition did not differ between Solanum species, which were preferred to other tested solanaceous plants. These results appeared to be consistent with survival rates and development times. Because larval survivability depends on the female’s oviposition choice, the hypothesis that host plant choice is influenced by plant volatile organic compounds has to be tested. Volatile organic compounds released by solanaceous plants were trapped using a dynamic collection system, and analyzed by GC-MS. Solanum volatile profiles showed similarities, and were presenting quantitative and qualitative differences with the other tested solanaceous plants, providing some explanations in the observed behavioral discrimination. Further electrophysiological and behavioral assays are required to confirm the effect of specific chemicals on the choice of the oviposition site in T. absoluta. It can be concluded that Solanum species are the more suitable hosts for T. absoluta development. Other solanaceous plant species could be opportunistically colonized with little incidence but care should be taken in these results as genetic variability in insects and plants, as well as plant physiological state, might have an impact on the pest survivability. [less ▲]

Innovative integrated pest management methods are needed to overcome market withdrawal of synthetic pesticides. Therefore, the identification of environment-friendly bio-products carrying direct or indirect biocide activity is one promising alternative option. Our researches focus on the identification of appropriate formulations releasing volatile organic compounds that are attractant for natural enemies of insect pests. However, the elaboration of slow-release devices that ensure stable and controlled release of active volatile compounds is quite challenging. Here, we developed a formulation based on E-β-farnesene and (-)-β-caryophyllene, these two semiochemicals having strong attractive potential on aphid natural enemies including lady beetles and hoverflies. Both compounds were encapsulated together in alginate gel beads. The blend efficiency was first evaluated through laboratory assays, and then in wheat and broad bean fields, by considering the abundance and diversity of aphids and their natural enemies. [less ▲]

Following the introduction of the invasive species Harmonia axyridis (Pallas) in Europe, many research works were conducted on its ecological, economic and social impacts. Recently, our team has been ... [more ▼]

Following the introduction of the invasive species Harmonia axyridis (Pallas) in Europe, many research works were conducted on its ecological, economic and social impacts. Recently, our team has been involved in the characterization of the behavioral traits making this lady beetle species so successful. The main conclusions of two PhD works will be shortly presented: (1) Through a six-year inventory performed in Belgian agroecosystems, we have demonstrated that H. axyridis has become well established and was among the most abundant aphidophagous predatory species, causing a severe depression of biodiversity, even if communities of aphid predators are still quite diversified. (2) The social issues associated with the establishment of overwintering aggregations in human constructions were also carefully investigated. We have demonstrated the importance of social interactions on the establishment and cohesion of the aggregates. Finally, we have demonstrated that the deposition of a set of saturated and non-saturated hydrocarbons on the surfaces where the lady beetles were settling on, allowed their conspecifics to follow their markings and join the group. [less ▲]

To date, volatile sex pheromones have not been identified in the Coccinellidae family; yet, various studies have suggested that such semiochemicals exist. Here, we collected volatile chemicals released by ... [more ▼]

To date, volatile sex pheromones have not been identified in the Coccinellidae family; yet, various studies have suggested that such semiochemicals exist. Here, we collected volatile chemicals released by virgin females of the multicolored Asian lady beetle, Harmonia axyridis (Pallas), which were either allowed or not allowed to feed on aphids. Virgin females in the presence of aphids, exhibited “calling behavior”, which is commonly associated with the emission of a sex pheromone in several Coleoptera species. These calling females were found to release a blend of volatile compounds that is involved in the remote attraction (i.e., from a distance) of males. Gas Chromatography Mass Spectrometry (GC-MS) analyses revealed that (–)-β-caryophyllene was the major constituent of the volatile blend (ranging from 80 to 86%), with four other chemical components also being present; β-elemene, methyl-eugenol, α-humulene, and α-bulnesene. In a second set of experiments, the emission of the five constituents identified from the blend was quantified daily over a 9-day period after exposure to aphids. We found that the quantity of all five chemicals significantly increased across the experimental period. Finally, we evaluated the activity of a synthetic blend of these chemicals by performing bioassays which demonstrated the same attractive effect in males only. The results confirm that female H. axyridis produce a volatile sex pheromone. These findings have potential in the development of more specific and efficient biological pest-control management methods aimed at manipulating the behavior of this invasive lady beetle. [less ▲]

The aphid–ant mutualistic relationships are not necessarily obligate for neither partners but evidence is that such interactions provide them strong advantages in terms of global fitness. While it is ... [more ▼]

The aphid–ant mutualistic relationships are not necessarily obligate for neither partners but evidence is that such interactions provide them strong advantages in terms of global fitness. While it is largely assumed that ants actively search for their mutualistic partners namely using volatile cues; whether winged aphids (i.e. aphids’ most mobile form) are able to select ant-frequented areas had not been investigated so far. Ant-frequented sites would indeed offer several advantages for these aphids including a lower predation pressure through ant presence and enhanced chances of establishing mutuaslistic interactions with neighbour ant colonies. In the field, aphid colonies are often observed in higher densities around ant nests, which is probably linked to a better survival ensured by ants’ services. Nevertheless, this could also result from a preferential establishment of winged aphids in ant-frequented areas. We tested this last hypothesis through different ethological assays and show that the facultative myrmecophilous black bean aphid, Aphis fabae L., does not orientate its search for a host plant preferentially towards ant-frequented plants. However our results suggest that ants reduce the number of winged aphids leaving the newly colonized plant. Thus, ants involved in facultative myrmecophilous interactions with aphids appear to contribute to structure aphid populations in the field by ensuring a better establishment and survival of newly established colonies rather than by inducing a deliberate plant selection by aphid partners based on the proximity of ant colonies. [less ▲]

Aphids are widespread insects considered as crop pest throughout the world. In order to control them, different techniques are known. The study of aphid-related semiochemicals is one topic recently ... [more ▼]

Aphids are widespread insects considered as crop pest throughout the world. In order to control them, different techniques are known. The study of aphid-related semiochemicals is one topic recently studied in integrated pest management, used to control aphid outbreaks. These semiochemicals include those involved in intraspecific communication, in communication among different trophic levels, those which attract or repel aphids, or those which enhance the efficiency of aphid natural enemies. This book chapter summarises the recent findings on aphid chemical ecology, from the discovery of molecules of interest, to their use in IPM methods. [less ▲]

The dynamic and impact of the major insect pests on Jatropha curcas L. were studied on two plantations located in the province of Kinshasa, the first in pure stand without irrigation (Mbankana site), the ... [more ▼]

The dynamic and impact of the major insect pests on Jatropha curcas L. were studied on two plantations located in the province of Kinshasa, the first in pure stand without irrigation (Mbankana site), the second under irrigation in combination with other crops (N'sele site). In Mbankana, after being planted during the long rainy season (October - December), the plants suffer significant attacks by crickets Brachytrupes membranaceus Drury (Orthoptera, Gryllidae), which cause a mortality rate of 10 - 40%. The first half of October and second half of December are the best planting periods when it comes to limiting these losses. At N'sele, cricket attacks during planting are controlled by the farmers who eat these insects. After being planted at both sites, the plants are attacked by leaf miner caterpillars Stomphastis thraustica Meyrick (Lepidoptera, Gracillariidae) and flea beetles Aphthona sp. (Coleoptera, Chrysomelidae), which consume the leaf blades and buds. The size of these two pest populations and resulting damage reach a peak during the wettest time of year. On adult plants at N'sele, insect pests observed include flea beetles, leaf miners, and shield-backed bugs Calidea sp. (Heteroptera, Scutelleridae). These bugs cause damage to flowers and capsules. In the absence of insecticide treatments, yield losses reached 90% in Mbankana and 60% in N'sele. The discussion focuses on what causes the different pest impact levels recorded between the cropping systems and methods used to limit the main types of damage caused by insects on J. curcas in the Kinshasa region. [less ▲]

We here introduce the book « The Malagasy silk moths: ecological and socio-economic challenges » published in 2013 by the Presses agronomiques de Gembloux (Belgium). This book reflects the achievements ... [more ▼]

We here introduce the book « The Malagasy silk moths: ecological and socio-economic challenges » published in 2013 by the Presses agronomiques de Gembloux (Belgium). This book reflects the achievements and scientific activities of the project "Sustainable Management and valorisation of the endemic silkworm Borocera cajani in forest areas in the Antananarivo region" funded by Commission universitaire pour le Développement (CUD - CIUF). [less ▲]

Insects are highly dependent on odor cues released into the environment to locate conspecifics or food sources. This mechanism is particularly important for insect predators that rely on kairomones ... [more ▼]

Insects are highly dependent on odor cues released into the environment to locate conspecifics or food sources. This mechanism is particularly important for insect predators that rely on kairomones released by their prey to detect them. In the context of climate change and, more specifically, modifications in the gas composition of the atmosphere, chemical communication-mediating interactions between phytophagous insect pests, their host plants, and their natural enemies is likely to be impacted. Several reports have indicated that modifications to plants caused by elevated carbon dioxide and ozone concentrations might indirectly affect insect herbivores, with community-level modifications to this group potentially having an indirect influence on higher trophic levels. The vulnerability of agricultural insect pests toward their natural enemies under elevated greenhouse gases concentrations has been frequently reported, but conflicting results have been obtained. This literature review shows that the higher levels of carbon dioxide, as predicted for the coming century, do not enhance the abundance or efficiency of natural enemies to locate hosts or prey in most published studies. Increased ozone levels lead to modifications in herbivore-induced volatile organic compounds (VOCs) released by damaged plants, which may impact the attractiveness of these herbivores to the third trophic level. Furthermore, other oxidative gases (such as SO2 and NO2) tend to reduce the abundance of natural enemies. The impact of changes in atmospheric gas emissions on plant–insect and insect–insect chemical communication has been under-documented, despite the significance of these mechanisms in tritrophic interactions. We conclude by suggesting some further prospects on this topic of research yet to be investigated. [less ▲]

Following the introduction in the 80's of the invasive coccinellid species Harmonia axyridis (Pallas) in Europe, several studies have begun to focus on the interactions with other aphid predator species ... [more ▼]

Following the introduction in the 80's of the invasive coccinellid species Harmonia axyridis (Pallas) in Europe, several studies have begun to focus on the interactions with other aphid predator species. In this study, aphids and associated predators were sampled to determine their relative abundance in four agricultural crops (broad bean, corn, potato, and wheat) in Belgium during 2010 and 2011. The Moericke trap was used to quantify the mean number of aphids and aphid predators from May to September in both years. A total of 28 aphid species and 21 aphidophagous species were observed. In both years, H. axyridis was among the most abundant aphidophagous predators in all four crops, and was the second most abundant coccinellid species after Coccinella septempunctata L. The community of aphidophagous species was similar across all four inventoried crops. However, the highest population densities of this alien species were recorded in broad bean and potato crops, which also hosted the highest aphid population densities. In conclusion, this study demonstrates that the communities of aphid predators are highly diversified in the agroecosystems, despite the high occurrence of H. axyridis, an introduced predator that has become well established in this environment. [less ▲]